Abstract
The transformation of wastewater treatment plants (WWTPs) into biorefineries capable of recovering value-added products represents a major opportunity to advance towards a circular economy. However, various structural and cultural factors are acting as significant barriers, hindering large-scale implementation. This issue was thoroughly addressed during the joint event of the European projects UPSTREAM and ReLEAF, held on 24 April and organised by Leitat, where experts from different fields discussed the main challenges and opportunities currently facing the sector.
One of the most significant problems lies in the structure of public procurement. In many cases, WWTP operation contracts are so short (typically four years) that it becomes unfeasible to amortise any substantial investment in innovative technologies. Faced with such a limited time frame, companies tend to opt for conservative solutions, avoiding the introduction of new processes which, although more sustainable or efficient, would require a higher initial cost. This situation is further worsened by restrictive legislation which, rather than encouraging innovation, often promotes specific technologies, limiting companies’ ability to choose alternative solutions. Policy makers also tend to adopt a conservative stance in this context. In the absence of immediate or easily demonstrable benefits and concerned about potential increases in the cost of current processes, they prefer not to take risks or introduce substantial changes. This mindset hampers the adoption of emerging technologies, even when their viability has already been demonstrated in R&D environments. According to organisations such as Global Omnium, it has been pointed out that the implementation of research project results in real WWTPs can be delayed over time due to economic and administrative barriers, slowing the sector’s progress.
Another critical aspect is the lack of public awareness regarding the role and functioning of WWTPs. While other sectors, such as the electricity sector, have managed to engage citizens through clear information on costs and benefits, in the water sector treatment plants are still perceived as a black box (where wastewater goes in and clean water comes out), with no real understanding of the processes involved or the challenges faced. This disconnection makes it difficult to generate the social pressure needed for authorities to prioritise more sustainable investments.
A final key aspect that could support the transition towards a circular economy and transform WWTPs into biorefineries is the strengthening of collaboration mechanisms between research centres and operating companies. Although in many cases technological developments reach high levels of maturity (TRL 6–7), actual implementation remains limited. As highlighted, there is no clear strategy for knowledge transfer nor a shared commitment to bringing innovation beyond the experimental stage. Public-private synergies, particularly in applied R&D projects, can act as a catalyst to bridge the critical gap between technological validation and industrial- scale adoption. Companies can provide a practical perspective, identifying real technical and economic barriers that may go unnoticed in academic settings. In turn, technological centres and universities contribute methodological rigour, analytical resources, and monitoring tools to ensure the feasibility and replicability of the process.
For this reason, it is essential to establish stable spaces for co-innovation and funding models that enable testing under real operating conditions in order to close the innovation loop. Only through structured collaboration will it be possible to scale up the most promising solutions. To make the deployment of true biorefineries within WWTPs feasible, action is needed on several fronts. Firstly, extending the duration of procurement contracts would allow companies to plan with a longer-term perspective and invest in innovative technologies without fearing for their profitability, while also fostering collaboration with research centres mentioned above. Secondly, more open legislation is required, one that does not impose fixed technological solutions but rather promotes technological flexibility and the achievement of clear environmental and economic targets. Finally, it is vital to raise public awareness by bringing the water sector closer to the population through outreach, training, and education campaigns.
Only with an informed and engaged society will it be possible to generate the momentum needed for a genuine transition towards a more sustainable, circular, and resilient water management system based on resource recovery technologies.
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